Those skilled in the art of automatic musical instruments are well aware of the various mechanisms which have been developed over the years to actuate the action of player and reproducing pianos. (It will be understood that a reproducing piano is a highly developed refinement of the player piano in that hand playing is closely reproduced by carefully controlling the dynamics and pedaling of the reproduction so as undertake to replicate the original performance of the artist.) For many years, the preferred actuator mechanism in player and reproducing pianos was the striker pneumatic array (known in the art as a "stack") operating under control of a suitable valve system reading a piano roll traveling across a tracker bar to selectively admit vacuum to individual striker pneumatics, thereby causing them to selectively collapse and correspondingly strike the individual action notes. These mechanisms reached their zenith in the best of the Welte, Ampico and Duo-Art reproducing systems installed in fine pianos. The Welte, Ampico, Duo-Art and a few other less well known reproducing systems included control units which provided instantaneous control of the vacuum intensity in separate bass and treble sections in order to control the dynamics of each note struck. By this arrangement, remarkable reproduction of an original performance can be obtained if the reproducing equipment and piano are in fine condition.
In recent years, several player and reproducing systems have employed striker solenoid stacks in place of the striker pneumatics. Such systems have included the Pianocorder.TM., Disklavier.TM., Pianodisk.TM., Bosendorfer SE.TM. ("Stahnke-Equipped") and Pianomation.TM.. The complex and expensive Bosendorfer SE system is widely thought to provide instant playback (and, of course, long term preservation) which is virtually indistinguishable from the original performance. The Pianomation system, also designed by Wayne Stahnke, is capable of providing a performance only slightly inferior in power to that of the Bosendorfer SE and, in some respects, offers even further refinement in nuance capability in a relatively inexpensive package suitable for retrofit into an existing instrument.
Those skilled in the art will understand that all these solenoid-actuated stacks suffer from as many as seven problems more or less in common with the old pneumatic stacks: viz.:
1) they are noisy due to either the use of solenoid coil bobbins which are dimensionally too unstable to permit a close tolerance between coil and slug or because the distance between the coil and keytail is so great that side forces on the necessarily long wire connecting solenoid slug and pusher tip make a guide necessary, that fact rendering it difficult to achieve close concentricity between this guide and the solenoid bore such that a loose fit is needed to prevent sticking of the slug in its coil tube;
2) they are difficult to install due to the need to: A) extensively modify a grand piano's pedal hardware to accommodate pedal linkages, different for each model of piano and B) make and slot a box and apply noise-muffling felt to the box;
3) in grand pianos, they are physically situated beneath the keybed in such a downwardly depending manner that the graceful lines of the piano are seriously compromised;
4) they require a more or less complex cohesive structure or framework in which to mount the key actuators. In order to have adequate power, the solenoids are too large to fit above the keybed; therefore some designers have placed the solenoids below the keybed such that, even in the typical front-to-back staggered arrangement, they still cause an unsightly downward protrusion from the keybed;
5) some designs do not allow the individual removal and replacement of a solenoid without disturbing others;
6) In retrofit form, it is difficult, time consuming and awkward to adjust the solenoids laterally to their respective keys; and
7) conventional vertically staggered stacks, which are not horizontally staggered also, placed a geometric limitation on the size of the coils used, thus inappropriately limiting the fortissimo capability of the system.
With great care in designing (including the incorporation of sound deadening material) and utilizing a solenoid-concealing housing, the noisy character of the stack can be diminished to a tolerable, if not completely acceptable, level; but this expedient, if anything, introduces a further intrusion on the aesthetics of the piano. In conjunction with the invention of my copending application Ser. No. 07/554,740, filed on even date herewith and entitled "SOLENOID MOUNTING SYSTEMS FOR PLAYER AND REPRODUCING PIANOS", it is to the interactive solution of all seven of the above problems that my invention is directed.